As oil-based ball-point pen ink compositions, oil-based ball-point pen ink compositions using various dyes such as nigrosine dyes have been conventionally proposed for offering deep written traces, in Japanese Patent Laid-Open No. 7-188601 “OIL-BASED BALL POINT PEN INK COMPOSITION”, Japanese Patent Laid-Open No. 8-157765 “OIL-BASE INK COMPOSITION FOR BALL-POINT”, and the like.
Further, Japanese Patent Laid-Open No. 6-313144 “OIL-BASE BALL-POINT PEN” discloses an oil-based ball-point pen that is allowed to have an ink viscosity of 100 mPa·S or less at a shear rate of 400 s−1 and an ink viscosity of 1000 mPa·S or more at a shear rate of 5 s−1 to offer a favorable feeling of writing.